1. Field of the Invention
The present invention relates to a die exchanging device for a punch press and to a turret punch press provided with such a die exchanging device.
2. Description of the Prior Art
In the prior art, a finite number of die sets are attached in a turret of a turret punch press, and the die sets are exchanged manually. Sometimes, an automatic die exchanging device is used to discharge die sets attached in the turret and to charge other die sets in the turret for next use.
The above mentioned conventional automatic die exchanging device includes a pair of arms; that is, a first arm for discharging die sets from the turret and a second arm for taking other die sets out from a die storage magazine.
Also, in the above mentioned conventional automatic die exchanging device the pair of arms only carry out discharging and taking out of a die set respectively from the turret and the die storage magazine at the same time and only exchanges the die sets. Therefore, it is necessary to exchange die sets several times when some die sets are required for one processing on a workpiece, and this takes much total time.
In addition, it is necessary to move the arms upwards and downwards since heights of the die storage magazine and a die set attached in the punch press for use differ from each other. Due to such movements of the arms, which is complicated, the die exchanging device requires large space and much time for exchanging of the die sets. Furthermore, the structure of the device becomes complicated for moving the arms, and, as a result, the exchanging device will cost much and take much time for possible repairing or maintaining.
Furthermore, in a conventional turret punch press with a die exchanging device, for example, a method for positioning and fixing a die set in the turret is generally used by pushing the die set to come into contact with a reference surface disposed on the turret and fixing it by means of a hydraulic pressing device.
In the above mentioned positioning and fixing method, the contact of the die set with the reference surface of the turret is surface-to-surface contact, and therefore it is difficult to cause the die set to come into uniform contact with the reference surface by reason of processing precision. Then, an error for positioning arises.
Furthermore, the hydraulic pressing device is disposed on the turret, arid therefore the punch press becomes complicated in structure and cost much, and it requires large space as a result. Moreover, time lag occurs, and maintenance becomes necessary for the use of hydraulic operation.